The present invention relates to a hydraulic actuating device for brakes and gearshifts of bicycles or the like and, in particular, to a device of the type that includes an actuating lever, a transmitting cylinder actuated by the lever, a receiving cylinder, and a flexible pressure line communicating the receiving cylinder and the transmitting cylinder, and that converts the displacement of the transmitting cylinder by the actuation of the actuating lever into displacement of the receiving cylinder in accordance with the diameter ratio between the transmitting cylinder and the receiving cylinder.
An actuating device of the type referred to above is known from, for example, French patent application 85 00 480 (Publication No. 2 575 991). In the actuating device of French Publication No. 2,575,991, a cylinder part of a receiving cylinder is directly connected with a first brake lever part, pivotally mounted on a bicycle frame, and a piston part, which is displaceably received in the cylinder part, is directly connected with a second brake lever part. When a brake handle is actuated, a working fluid is pressurized by the displacement of a piston in a transmitting cylinder and the pressurized working fluid is delivered from the transmitting cylinder. The transmitting cylinder is connected by a hydraulic pressure line with a pressure chamber in the receiving cylinder, so that the working fluid delivered from the transmitting cylinder results in an increase in the amount of working fluid in the pressure chamber of the receiving cylinder. As a result, the piston disposed in the receiving cylinder is displaced by the pressure of the working fluid in the pressure chamber of the receiving cylinder, so that the total length of the receiving cylinder-piston arrangement is increased, whereby the first and second brake lever parts of the bicycle brake are pivoted in respect to each other and in this way result in a braking action.
The known brake device has the disadvantage that it is designed for a force transfer, for example, to the brake lever parts, only through pressure action and that it is designed specially for such brake lever parts. It is required in each case to specially design and manufacture these actuating devices structurally for use as an actuating device for other elements to be operated, thereby resulting in high manufacturing costs, which are particularly crucial in the field mass produced bicycle accessories.
Furthermore, an actuating device for bicycle brakes is known from German Published, Non-Examined Patent Application DE- A-33 03 586, wherein a receiving cylinder is also disposed between two brake lever parts that are pivotally mounted on a bicycle frame, and wherein the increase of the working fluid pressure in a pressure chamber results in an increase of the total length of the-receiving cylinder-piston unit, so that the brake lever parts are again pivoted and result in a braking action. In that known device, too, the receiving cylinder-piston unit is specially designed for use with brake lever parts. A special, different type of design of the receiving cylinder-piston unit is required for use with other components or with brake lever parts of different lever arm lengths, because of which the manufacturing costs for this device are also relatively high.